1. Field of the Invention:
The present invention relates to an apparatus for continuously thermally treating elongate textile products such as yarns, tapes, ribbons, or the like.
2. Description of the Prior Art:
Textile products generally contain oil since their yarns are oiled when they are twisted, woven, or knitted. At the time such an oiled textile product is thermally treated, or heated, in the housing of a heat treatment apparatus, the oil in the textile product becomes an oily smoke that is deposited as tar on the textile product and the inner wall surfaces of the housing, thereby contaminating them. If such oily smoke leaks out of the housing, the working environment for the operator or operators around the housing becomes poor. Various attempts have heretofore been made to prevent oily smoke from being enriched in the housing. One proposed process has been to discharge part of hot air circulating in the housing and introduce fresh air into the housing. Before the hot air is discharged from the housing, it is guided to flow through a heat exchanger to retrieve waste heat therefrom. When oily smoke in the hot air is brought into contact with fresh air in the heat exchanger, it is cooled and deposited as tar in the heat exchanger. The deposited tar should be removed periodically by shutting off and disassembling the heat treatment apparatus to clean up the heat exchanger for effective operation. Such periodic shutdowns however result in a reduction in the production rate.
The housing of the heat treatment apparatus is required to be thermally isolated from the external environment. To meet this requirement, the inlet or outlet of the housing is connected to a low pressure chamber for preventing cold external air from entering the housing through the inlet or outlet. One such an arrangement is known from Japanese Patent Publication No. 47(1972)-21276 as illustrated in FIG. 3 of the accompanying drawings. The low-pressure chamber, denoted at A, is coupled to the inlet of the housing, and is supplied with heated air under pressure which is used for thermally treating the elongate textile article. The pressure in the low-pressure chamber is equalized to or higher than the atmospheric pressure to prevent cold external air from being drawn into the housing through the inlet. The above conventional housing design is however disadvantageous in that heat consumption by the overall apparatus is increased and hence the cost is high since part of the heated air in the housing is utilized to avoid entry of air for thermal isolation of the housing. Where the textile product being heat-treated is an oiled article, generated oily smoke tends to flow together with the heated air out of the housing through the inlet and outlet thereof, resulting in environmental contamination.